Patent Document 1 (Japanese Patent Application Laid-open Publication No. 2008-041465) suggests such a combination as selecting a lithium nickel cobalt manganese composite oxide as an active material to be used for a positive electrode and as selecting an easily graphitizable carbon as an active material to be used for a negative electrode, in order to achieve a high input/output density and excellent cycle characteristics.
Patent Document 2 (Japanese Patent No. 5168593) suggests the combination of the active material to be used for the positive electrode and the active material to be used for the negative electrode, which are similar to those of Patent Document 1, in order to ensure the cycle characteristics and storage characteristics.
Further, Patent Document 3 (Japanese Patent No. 5578341) suggests the combination of the active material to be used for the positive electrode and the active material to be used for the negative electrode, which are similar to those of Patent Document 1, in order to improve the input/output characteristics at a low temperature.